| Herein we discuss a number of advances in both understanding and application of collinear and orthogonal dual-pulse LIBS (DP LIBS) during the past several years. Chapter one is a broad overview of recent DP LIBS literature and, in addition to discussing current and future directions of research, serves as both an introduction to and a summary of the remainder of this work. Chapter two uses orthogonal femtosecond- (fs) and nanosecond-pulse (ns) laser-induced plasmas (LIPS) in both pre-ablative spark and reheating configurations as a "first pass" at attempting to determine possible sources of DP LIBS' atomic emission and signal-to-noise enhancements, and indicates potential contributions vial atmospheric number density reductions, atmospheric heating, sample heating, and direct plasma-plasma coupling effects. Chapters three through five further examine the importance of these effects in orthogonal fs-ns DP LIBS, and chapter six extends our work to the collinear fs-ns dual-pulse configuration---all four studies verify the potential significance of the aforementioned effects in both collinear and orthogonal DP LIBS.; As a result of these studies, it is now clear that a full examination of both optimal and non-optimal DP LIBS enhancements is necessary to determine the relative importance of atmospheric concentration, sample heating, and plasma-plasma coupling effects. With the identification of these factors, the LIBS community should now be able to more rapidly advance both understanding and application of collinear and orthogonal DP LIBS. |
